1. Field of the Invention
The present invention relates to an organic transistor and associates, and, in particular, to an organic thin-film transistor having light emission function, as well as a display device employing it.
2. Description of the Related Art
Along with a spread of each type of information terminal unit, an improvement of performance and a variety of the devices are demanded. Specifically, needs for a flat panel display device as a display device for a computer has been increasing. Further, along with a development of information society, occasions of providing information in an electronic form instead of a form of paper has been increasing. Thereby, needs for an electronic paper or a digital paper as a mobile display medium which is thin and has a light weight, so that it is easier for carrying, are increasing.
Generally speaking, a display medium employing a device of liquid crystal, organic EL, electrophoretic effect or such, is provided in a flat-type display device. In such a display medium, in order to ensure uniformity of screen brightness and/or screen rewriting speed, an art of using an active driving device made of a thin-film transistor (TFT) is mainly employed for the image driving device. The TFT device is produced as a result of, commonly, on a glass substrate, mainly a semiconductor thin-film such as that of a-Si (amorphous silicon), p-Si (polysilicon) or such, a metal thin-film for a source, a drain and a gate electrodes, and so forth, being laminated in sequence. For producing a flat-panel display device employing the TFT device, commonly, in addition to a thin-film producing process employing a vacuum equipment for CVD, spattering or such, a high-temperature processing process and so forth, a photolithographic process requiring a high accuracy, are required. Therefore, equipment costs and running costs may become very high. Further, along with recent needs for an increase in a size of the display screen, a cost increasing rate along with manufacturing it has becomes very high.
Recently, research and development of an organic TFT device employing an organic semiconductor material is proceeded with (see Japanese Laid-open Patent Application No. 10-190001 and the Advanced Materials journal, 2002, No. 2, page 99 (review)). According to SID, '02 Digest, page 57, since the organic TFT device can be produced in a low temperature process, a resin substrate which has a light weight and is hard to be broken, can be employed instead of a glass substrate which has a heavy weight and is easy to be broken. Further, according to the same document, a flexible display device employing a resin film as a supporting body will be realized. Further, as a result of employing an organic semiconductor material which can be produced in a wet process such as printing, coating or such under an atmospheric pressure being employed, a display device of a very reduced cost with a superior productivity can be realized.
On the other hand, as part of research result of such an organic TFT device employing organic semiconductor material, a light emitting type transistor is reported (see Extended Abstracts (The 65th Autumn Meeting, 2004), Japan Society of Applied Physics, page 1163). By using it, a display device having a new configuration in which a display medium and an image driving device can be integrated, may be realized.